Process of hardening protein substances



Patented Apr. is, 1939 PATENT OFFICE amassmoons s or naannnmo morals soasrancss Hans Fricke, Wolfen, Kreis Bitterfeld, and Johanlies en,

Dessan, Germany, assignors to Asia Ansco Corporation,.Blnghamton, N. Y., a corporation of New York No Drawing. Application June is, 1938, Serial No. 213,449. In Germany June 19, 1937 11 Claims.

The present invention relates to an improved process of hardening protein substances and more particularly to the hardening of photographic silver halide gelatin layers.

5 It is known practice to harden photographic silver halide emulsion layers by treatment with an aldehyde, and for this purpose formaldehyde has mainly been used. Other known hardening aldehydes are: glyoxal, dibromoacrolein, oxyalde- 1 hyde. By addition of these aldehydes to photographic emulsions, however, there is produced, particularly when a large proportion is used in order to obtain a high degree of hardening, a diminution of the threshold sensitivity.

15 It is an object of the present invention to provide a process of hardening protein substances and simultaneously increasing the threshold sen sitivity, so that the disadvantage hitherto accomcals. 30 Other objects are set forth in the following specification.

Examples of aldehyde carboxyilc acids suitable for the invention are g'lyoxylic acid, glyoxyl-m'o-r pionic acid, glyoxyl-isobutyric acid, formyl- 36 acrylic acid, formyl-acetic acid, p-formyl-propicnic acid, and 'y-formyl-butyric acid. 'By substitution, especially by introduction of hydroxy-, ketoor amino-groups, there is moveover obtained a large number of new, valuable aldehyde car- 40 boxylic acids suitable for hardening. Halogen is not suitable as a substituent because it effects no or only a very slight-increasing of the. threshold sensitivity. By halogenated aldehyde carboxylic acids there is also obtained a flatten- 45 ing of the gradation.

The application of the new hardening agents follows the method usual in photographic practice. The hardening agents may be added to the washing emulsion shortly. before the casting op- 50 eration; they may also be'added to the cast layer in the undeveloped or developed condition by treating the layer in a bath containing the sublulose, cellulose derivative or metal. The application of the new hardening agent is not limited to the actual photographic silver halide emulsion; it may also be used to harden an under-layer or an over-layer or a backing layer, also inter- 5 mediate layers and preparatory layers of gelatin or other protein bodies or mixtures of such' with other colloids. The preparation of the mixture to be used varies somewhat according to the melting-point desired. In general 50-5000 milli- 1 grams per kilo of a gelatin solution of about per cent strength is desirable, but the invention is not limited to such preparation. Among other protein layers which can be hardened by the new agents may be named albumen, casein, and gliadine.

The following examples illustrate the invention:

Example 1 1 kilo of gelatin silver halide emulsion for negative purposes, having a gelatin content of about 8-9 per cent, and optically sensitized by means of a dyestuif, is mixed in molten condition with 200 milligrams of formylacrylic acid and then cast in the usual manner, The dry layer melts at 36 0.. while the unhardened layer melts at 33 C. The increase of threshold sensitivity is about '75 per cent. In the course of storage the layer-becomes somewhat harder.

1 kilo of a silver halide emulsion containin 8-9 per cent of gelatin and intended for Roentgen exposure is mixed with about 400 milligrams of 5 neutralized 'glyoxylic acid and then cast. The increase of theshold sensitivity amounts to 50-75 per cent. The melting point of the dry layer is 34 C., while the melting point of the unhardened layer is only 32 0. During storage the melting 40 point increases somewhat.

Example 3 Example 4 1 kilo of gelatin silver halide emulsion having a gelatincontent of about 8-9 per cent is mixed with 350 milligrams of 'y-iormyl-butyric acid and then cast. The melting point 0! the dry layer 2. A process which comprises bathing a photo graphic material consisting of a support and a gelatin layer in a solution of a compound selected from the class consisting of an aliphatic non-substituted aldehyde carboxylic acid and an aliphatic aldehyde carboxylic acid containing in itsmolecule a member selected from the class consisting of a hydroxy group, a keto group, and an amino group.

3. A process which comprises adding to a photographic silver halide gelatin emulsion containing about 10 per cent of gelatin 0.005 to 0.5 per cent of a compound selected from the class consisting -of an aliphatic non-substituted aldehyde carboxylic acid and an aliphatic aldehyde carboxylic acid containing in its molecule a member selected from the class consisting of a hydroxy group, a keto group, and an amino group.

4. A process which comprises adding to a photographic silver halide gelatin emulsioncontaining 8 to 9 per cent of gelatin 0.02 per cent of formylacrylic acid.

5. A process of hardening a protein substance which comprises treating it with acompound selected from the class consisting of an aliphatic non-substituted aldehyde carboxylic acid and an aliphatic aldehyde carboxylic acid containing in its molecule a member selected from the class consisting of a hydroxy group, a keto group, and an amino group.

6. A process of hardening gelatin which comprises treating it with Iormyl-acrylic acid.

7. A process of hardening gelatin which comprises treating it with glyoxylic acid.

8. Gelatin hardened by the addition oi. and

- containing a compound selected from the class consisting of an aliphatic, non-substituted aldehyde carboxylic acid and of an aliphatic aldehyde carboxylic acid containing in its molecule a' member selected from the class consisting of a hydroxy group, a keto group and anamino group.

9. A photographic silver halide emulsion layer containing gelatin and a compound selected. from the class consisting of an aliphatic non-substituted aldehyde carboxylic acid and of an aliphatic aldehyde carboxylic acid containing in its molecule a member selected from the class consisting of a hydroxy group, a keto group and an amino group.

10. A photographic silver halide emulsion layer containing gelatin and formyl-acrylic acid.

11. A photographic silver halide emulsion layer containing gelatin and glyoxylic acid.

. HANS FRICKE.

JOHANNES BRU'NKEN. 

